title: Homologous challenge of porcine reproductive and respiratory syndrome virus immunity in pregnant swine.
abstract: The clinical consequences of single or multiple exposure of pregnant gilts to porcine reproductive and respiratory syndrome virus (PRRSV) at various stages of gestation were determined. Thirty-three pregnant gilts were allotted to 6 experimental groups (5 to 7 gilts/group). Gilts of groups 1 to 5 were exposed to strain NADC-8 of PRRSV at the following times: group 1, gestation day (GD) 1; group 2, GDs 1 and 90; group 3, GD 30; group 4, GDs 30 and 90; group 5, GD 90. Virus exposure was by either intrauterine (GD 1) or oronasal (GDs 30 and 90) inoculation. Gilts of group 6 were kept as nonexposed controls. Gilts were either necropsied on or about GD 111 (groups 1 to 5) or were allowed to farrow (group 6). The detection of PRRSV in serum of fetuses and piglets (within 12 hof birth) was considered evidence of transplacental infection. Transplacental infection and virus-induced death were and were not confirmed for groups 3, 4, and 5 and for groups 1, 2, and 6, respectively. Collectively, the results indicated that intrauterine exposure to PRRSV at GD 1 was without clinical effect (groups 1 and 2) and provided protection against subsequent exposure to the same strain of virus at GD 90 (group 2). The highest incidence of transplacental infection and fetal death followed a single exposure to PRRSV at GD 90 (group 5).
authors.affiliation: Virology Swine Research Unit, National Animal Disease Center, USDA, Ames, IA 50010, USA. klager@nadc.ars.usda.gov
authors.forename: K M
authors.initials: KM
authors.lastname: Lager
authors.forename: W L
authors.initials: WL
authors.lastname: Mengeling
authors.forename: S L
authors.initials: SL
authors.lastname: Brockmeier
mesh_terms: D000818:Animals; D005260:Female; D005333:Fetus; D005865:Gestational Age; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary*; D008198:Lymph Nodes / Q000821:virology; D017737:Macrophages, Peritoneal / Q000821:virology; D014066:Palatine Tonsil / Q000821:virology; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology* / Q000302:isolation & purification; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D011270:Pregnancy, Animal / Q000276:immunology*; D013552:Swine; D013997:Time Factors; D014599:Uterus